Differential pneumatic hoist



L. PERAS DIFFERENTIAL PNEUMATIC HOIST Sept. 29, 1959 '3 Sheets-Sheet 1 Filed Dec. 7, 1955 3 Sheets-Sheet 2 Sept. 29, 1959 L. PERAS DIFFERENTIAL PNEUMATIC HOIST Filed Dec. '7, 1955 Sept. 29, 1959 1.. PERAS 2,906,248

DIFFERENTIAL PNEUMATIC HOIST.

Filed Dec. 7, 1955 3 Sheets-Sheet 3 United States Patent M DIFFERENTIAL PNEUMATIC HOIST Lucien Peras, Billancourt, France, assignor to Regie Nationale des Usines Renault, Billancourt, France Application December 7, 1955, Serial No. 551,625

Claims priority, application France May 13, 1955 4 Claims. (Cl. 121-46) The invention relates to a jack or hoist of the differential type specially intended for load-handling operations in manufacturing workshops. It has the advantage of forming an apparatus of reduced overall dimensions, supplied with compressed air through a single, fixed pipeline, the control distributing valve of the jack being, moreover, in the immediate vicinity of the hook bearing the load to be manipulated. A very handy apparatus is thus obtained.

According to the invention, the cylinder of the hoist, a hollow piston rod and an axial conduit contained in said rod form three concentric chambers. The outer chamber is constantly supplied with compressed air from one side of the piston and is in communication with the intermediate chamber, while the axial conduit, which leads into the cylinder above the piston, can be connected to the atmosphere or communicate with the intermediate chamber depending on the positions of a reverser-distributor provided at the end of the piston rod which is connected to the load in such a manner that placing the axial conduit in communication with the atmosphere controls the displacement of the piston in one direction by the escape of air on one side of the piston, while the admission of compressed air through the axial conduit to the same side, of the piston controls the displacement in the opposite direction as a result of a difference in the surfaces subjected axially above and below the piston to the air pressure.

A pneumatic hoist according to the invention will now be described by way of non-limiting example, with reference to the accompanying drawing, in which:

Figure 1 is a general view of a handling device equipped with a hoist according to the invention;

Figure 2 is a longitudinal view of said hoist partly in section;

Figure 3 is an axial sectional view one type of realiza' tion of the piston in the hoist;

Figure 4 is a side view, partly in section, of a different embodiment of the hoist;

Figure 5 is a sectional view of a packing ring having a single-lateral lip and peripheral grooves and usable in the hoist according to the invention;

Figure 6 is a perspective view of half of a packing ring;

Figure 7 is a fragmentary, sectional, side elevation View of a piston according to the invention, using the packing ring in Figure 6.

The hoist according to the drawings comprises a tube 1, which forms the cylinder, and is closed by two cylinder ends 2 and 3 joined together by rods such as 4. The end 1a comprises a lug 5 traversed by a pivot 6 by means of which the hoist is connected to its support 7.

On the inside, the end In comprises a central chamber 8 which forms an extension of the cylinder, and communicates with the cylinder 1 both through its open end and through the passageways 9 and 10. The latter passage may be restricted by means of the regulating screw 11. Two packingrings 12 and 13 eiiect the sealing respectively inside the central chamber and around the regu- 2,906,248 Patented Sept, .29, 1959 lating screw 11. Two packing rings 14 and 15 are provided between the cylinder 1 and its two heads.

The end 3 of the cylinder likewise comprises a central chamber 16 which communicates with the cylinder through the passageways 17 and 18 restricted by a regulating screw 19. Two packing rings 20 and 21 effect the sealing in the positions indicated. Screwed into the cylinder head 3 is the body of a non-return valve 22 to which is fixed, by means of a connection 23, an air-inlet tube 24. The tube is rigidly connected to the jack and is connected by means of a flexible pipe to a compressed air network. Screwed into the body 22 is a seat 25, a non-return valve 26 being placed between the seating and the conduit 18. The non-return valve 22--26 comprises a floating valve member comprising a hollow cylinder, as shown, having the end toward seat 26 partially closedofi in that the end thereof is provided with axial apertures and the opposite end is open. Accordingly air may flow through the passageways shown in valve body 22 through the floating member and through duct 18 into the interior of cylinder 1. However, in the event of loss of air pressure in the air system conduit 24 the air in the cylinder forces the hollow cylinder member against seat 25 closing off the axial apertures and the passageway in the body retaining the air pressure in the cylinder 1.

In the cylinder 1 there is disposed a reciprocable piston comprising two axial extensions of reduced diameter. The piston consists of three annular members 27, 28 and 29, the members 28 and 29 gripping a packing ring 30.

This piston is mounted on a hollow piston rod 31 which slides in a stufling-box nut 32 screwed into the cylinderend 3. The nut 32 carries a fixed packing ring 33 and a scraper ring 34. Between the nut 32 and an annular supporting member 35 there is provided a seal shown diagrammatically at 36.

Inside the hollow rod 31 is provided a tube 37, the annular chamber 38, thus formed, is bounded at the two ends by packing rings 39 and 40. The rod 31 is screwed into a reverser-distributor 41 which forms a fork 42 for a pivot 43 from which the load to be manipulated may be suspended by means of a hook 43a (Figure 1) for example; A nut 44 locks the member 41.

The central tube 37 leads into a passageway or duct 4546 provided in the reverser-distributor, while the chamber 38 is in communication with the duct 47. The passageways 46 and 47 lead into a rotary distributor slide 48, known in itself, which, depending on its position, enables the passageway 46 to be connected to the atmosphere or to the passageway 47. The handle 49 enables said slide to be operated by rotation in a plane perpendicular to the plane of the drawing. Annular seals 50, 51, 52 and 53 are arranged respectively between the body of the reverser-distributor and the hollow shaft, between the cap 54 and the body 42 and between said cap and the operating shaft 55.

The operation of this hoist is as follows:

The passageway 18 is constantly supplied with compressed air derived from the conduit 24, so that the valve 26 is held in the position illustrated on the drawing. If, for any reason, the pressure of the supply to the jack fails, the air contained in the jack pushes the valve against the seat 25 as stated heretofore which makes it impossible for air to escape through the conduit 24 and for the piston rod to drop suddenly. The rod 31 is also provided with an aperture 56 which brings the chamber 57 under the piston into communication with the chamber 38 which is therefore constantly supplied with compressed air.

When the hook of the hoist is to be raised, the handle 49 of the reverser-distributor is brought into the position illustrated in the drawing. In this position, the slide 48 brings the conduit 46 into communication with the atmosphere. Since the pressure of the compressed air acts upwardly on the piston, the piston rises and drives out the air contained in the chamber 58. This air escapes as the piston rises, through the conduit in the central tube 37, the conduits 4546 and the distributor slide 48, to the atmosphere. When the member 27 approaches the internal face of the cylinder end 2, the air contained in the chamber 58 can no longer escape except through the restricted orifice 9 and the stroke of the piston is slowed down. The assembly thus acts as a damping device.

When it is desired to lower the hook of the jack, it is necessary to reverse the position of the operating handle 49 so as to bring the conduits 47 and 46 into communication. The air pressure obtained in the annular chambers 57 and 38 (as a result of the aperture 56) is therefore likewise established in the central tube 37 and the upper chamber 8. The pressure likewise rises in the conduit and the piston moves down as a result of the greater surface exposed to the pressure obtained above the piston. The piston moves down slowly at first, and then more rapidly as soon as the member 27 has left the central chamber 8. Its movement is damped at the bottom of its stroke in the manner previously described for the top of its stroke.

Mounted on the inner ends 2 and 3 of the cylinder are annular stops of rubber 59 and 60 which protect the piston in the event of faulty operation of the damping device, since the piston then abuts against these rings at the end of its stroke.

According to another type of construction, the packing ring 30 may be replaced by a packing ring 61. More over, the annular seals 12 and 28 (Figure 1) may be omitted and it is then necessary to provide on the members 27 and 29 (Figure 2) or on the piston portions 62 and 63 (Figure 3) packing rings with a lateral lip and peripheral grooves 64 and 65 (Figure 3) which have likewise been described in detail in the said patent application.

Another embodiment of the hoist, according to the invention, is illustrated in Figure 4. This modification differs from the device in Figure 2 in the cylinder ends 66 and 67 which do not comprise the slow escape conduits 9, 10, 17 and 18, or the regulating screws 11 and 19 of the embodiment in Figure 2. On the other hand, the piston 68 consisting of a single part, carries two piston rings 69 and 78 mounted in opposite directions to one another, and two packing rings 71 and 72 mounted on the extensions of the piston, said four rings are of the type with a single lateral lip and peripheral grooves as shown.

Between the seats 73 and 74 for the piston rings 69 and 70 there is provided an annular chamber 75.

This hoist is damped at the end of the stroke in the following manner. When the piston 68 approaches the upper end, for example, of the cylinder 1, the packing ring 71 comes into contact with the wall of the chamber 76 in the cylinder end 66. The air contained in the annular space formed by the piston 68, the cylinder end 66, the upper extension of the piston and the cylinder 1 is then compressed. As the piston continues its stroke, the pressure of the air in the annular chamber increases, slowing down the movement of the piston, and finally reaches a value equal to that of the pressure in the chamber 77.

At this moment, the lip 78 of the packing ring 69 yields and the compressed air enters the chamber 75 between the packing rings 69 and 70. When the piston has almost reached the end of the cylinder, the annular chamber formed by the members 68, 66 and 1 becomes very small, the air which it contained having passed almost entirely into the chamber 75.

Thus the pressure of the damping air remains at a reasonable value, said value depending on the volume of the chamber 75. It being understood that chamber or annular recess is never under excessive pressures since the ratio of chamber 75 to the space between members 1, 66 and 68, as the piston moves toward member 66 at the end of its stroke, is such that excessive pressures cannot be built up. The same is true of the space formed at the opposite end of the stroke. This embodiment also has the advantage of permitting the omission of the needle regulating screw, the pneumatic damping depending only on the construction of the hoist and being provided in such a manner as to prevent the piston from striking at the end of its stroke. At the same time the risk of deterioration in the packing rings is reduced.

As shown in Figure 4, a packing ring 79 of the type described in the United States patent application Serial No. 551,627, filed December 7, 1955, in the name of the applicant, for Packing Ring, may replace the ring 36 in Figure 2.

The omission of the damping regulation by means of a needle valve is made possible by fitting the piston of the hoist with cup-shaped packing rings. A ring of this type is illustrated in Figure 6. It will be seen that this ring is made in the form of a cup, the sides of which widen out slightly, so as to form a truncated cone.

As shown in Figure 7, the hollow piston rod carries, in this embodiment, a piston formed by two supporting members 80 and 81, guided in the cylinder and provided with peripheral grooves 80a and 81a. Each supporting member carries a packing ring 82 or 83 with a single lateral lip and peripheral grooves. A central member 84 which is provided on its periphery with a circular chamber 85, is supported or disposed between members 80 and 81 jointly forming the piston. Between the members 80 and 84 on the one hand and the members 81 and 84 on the other hand, are gripped two cup-shaped packing rings 86 and 87.

This device operates similarly to the device in Figure 4, that is to say it permits the omission of the escape conduits and needle valve. Actually, assuming, for example, that the piston 8081-84 in Figure 7 is moving down, the compressed air in the annular chamber 88 will damp this descent. But when the air contained in the chamber 88 is above a certain pressure, the lip 89 of the packing ring 87 yields and the compressed air in 88 escapes through the grooves in the member 81 into the chamber 85, thus limiting the maximum damping pressure which can result from the displacement of the piston. The operation is obviously the same when the piston is rising.

I claim:

1. A pneumatic hoist of the differential type comprising a cylinder, means closing opposite ends of the cylinder and defining first and second chambers of lesser diameter than the cylinder and disposed at opposite ends of the cylinder and communicating with the interior thereof, a piston reciprocable in the cylinder, said piston having a central body portion and axial extensions of reduced diameter arranged at opposite ends of said body portion to enter both of said chambers as the piston approaches the end of its stroke thereby to cushion the piston, a hollow piston rod centrally connected to the piston and extending axially through the piston terminating at one end of a first axial extension of the piston and extending externally at one end of the cylinder opposite to said first axial extension, a tubular member defining a fluid conduit disposed axially in said rod and spaced radially from the inner walls of the hollow piston rod and extending through the piston terminating at a crown surface of the first axial piston extension to provide communication with said interior of the cylinder, means sealing each end of the piston rod thereby forming a third chamber between the rod and the axially disposed tubular member, the rod being provided with a hole providing communication between the third chamber and a space formed between the cylinder and the piston face on the side opposite the first axial extension,

a single air supply line connected to the cylinder and adjacent the end through which said piston rod extends for constantly supplying air pressure to the cylinder interior, a non-return valve connected between said line and the cylinder to preclude exhausting the cylinder in the event of loss of air pressure, a manually operated fluid distributor valve connected at the end of the piston rod extending axially through one end of the cylinder and carried thereon, said valve having fluid passageways communicating between the atmosphere and the axial conduit defined by said tubular member and between the conduit and the third chamber and having rotary valve means having a first operative position for providing communication between the atmosphere and the conduit simultaneously closing the passageway between the third chamber and the conduit and a second operative position for connecting the passageways for communication between the conduit and the third chamber and closing ofl communication with the atmosphere, whereby when the rotary valve means is placed in said first position the piston moves in a direction toward the cylinder end opposite the end through which said rod extends and remains in at the end of its stroke while said first position is maintained and when the rotary valve means is in the second position the piston moves in the opposite direction and remains at the end of its stroke in said opposite direction while said second position is maintained.

2. A pneumatic hoist of the differential type according to claim 1, in which means for connecting a load to the piston rod are provided, said last mentioned means being disposed adjacent the distributor valve.

3. A pneumatic hoist of the differential type according to claim 2, in which said means closing the opposite ends of the cylinder and defining the first and second chambers are provided with restricted passageways internal of the cylinder and in communication with the interior thereof and variable means for varying fluid flow through said restricted passageways thereby to vary cushioning of the piston.

4. A pneumatic hoist of the differential type according to claim 1, in which said piston central body portion is provided with an annular recess of a selected dimension, said piston having two rings constructed of a yieldable material and disposed on said central body portion axially of said recess on opposite sides thereof, each of said rings having an annular lip portion extending in a direction toward one another and slidable on the inner walls of the cylinder forming a fluid-tight seal between the cylinder walls and the piston, each of said annular lip portions having the characteristic of yielding separately to allow air flow to the annular recess when a given air pressure obtains in a corresponding end portion of the cylinder, and said given air pressure corresponding to an air pressure greater than the pressure provided by said supply line and corresponding to an air pressure obtaining when the piston is substantially at the end of each stroke thereof, whereby the piston is cushioned at the end of each stroke.

References Cited in the file of this patent UNITED STATES PATENTS 675,112 Rutherford May 28, 1901 702,979 Martin June 24, 1902 840,877 Steedman Jan. 8, 1907 845,827 Steedman Mar. 5, 1907 2,601,157 LeLan June 17, 1952 2,642,845 Stevens June 23, 1953 2,688,825 Montanus Sept. 14, 1954 2,719,510 Elder Oct. 4, 1955 

